X-ray Photon Electron Spectroscopy Research Articles

Microwave-Assisted Synthesis of Nitrogen-Doped Carbon Catalysts for Oxygen Reduction Reaction with Tunable Selectivity

The oxygen reduction reaction (ORR) is the core reaction in electrocatalysis systems such as fuel cells, metal-air batteries and hydrogen peroxide (H2O2) electro-generation. The ORR reaction mechanism has two possible pathways, namely, two-electron (2e−) or four-electron (4e−) processes that enable a reduction of oxygen into H2O2 or water (H2O), respectively. Both paths are useful where the former can provide on-site direct production of H2O2 and the latter is desired in fuel cells and batteries since it enables higher energy efficiency. Optimal ORR electrocatalyst should exhibit high activity, selectivity, stability, and low cost. Carbon materials modified with heteroatoms (e.g. nitrogen (N)) are considered potential alternatives for costly noble metal catalysts including Pt for ORR in fuel cells, and Au for the ORR to H2O2 (1,2). The typical synthesis procedure for the porous nitrogen-doped carbons (N–C) is based on the single or multiple pyrolysis steps of nitrogen-rich carbon precursor. The reactions required a pyrolysis step at the temperature range of 500-1200 °C and timing of one to tens of hours. Such processes showed a highly negative environmental impact due to high energy consumption. The production of 1 ton of activated carbon from lignocellulosic biomass feedstock requires 669.83 kWh (equivalent to an emission of 62.78 tons of CO2) (3). The synthesis of the N–C by microwave (MW) irradiation can reduce energy usage and ensure a more environmentally sustainable and economically viable approach. This procedure necessitates non-transparent materials to electromagnetic waves that can convert MW energy into heat and simultaneously enable the carbonization of the starting material.This work investigated the electrocatalytic activity towards ORR for N–C–MW catalysts derived from polyaniline (PANI) prepared in a one-step MW carbonization approach. PANI was selected due to two reasons: (i) N–C made by thermal pyrolysis of PANI showed improved electrocatalytic activity toward ORR where both the 4e− and the 2e− electron transfer pathways are feasible depending on the nature of active sides (4), (ii) PANI displayed good MW adsorption properties (5). The work aimed to identify the influence of the MW reaction condition on the resulting structure of the N–C–MW and the direction of the ORR. The N–C–MW samples were prepared under MW power of 450 and 800 W and time of 70, 140 and 210 s. The ORR activity of N–C–MW samples was investigated by cyclic voltammetry in the alkaline media (O2-saturated 0.1 M KOH). The experiment was performed in a three-electrode configuration composed of a rotating ring (Pt)–disk (glassy carbon) electrode (RRDE), a graphite rod as the counter electrode and a reversible hydrogen electrode (RHE) as the reference electrode. An influence of catalyst loading on disk electrode (0.05, 0.1 and 0.2 mg/cm2) was analyzed. All investigated MW reaction conditions resulted in the formation of porous disordered carbon structures with nitrogen and oxygen functionalities confirmed by X-ray photon-electron spectroscopy. The shorter time (70 s) and lower power (450 W) of MW treatment resulted in the formation of structures with a low carbonization rate and simultaneously a relatively poor catalytic activity for ORR (an onset potential of ∼0.65 V vs RHE). The samples carbonized under moderate (power of 450 W and 800 W, time of 140 s) and severe (power of 450 W, time of 210 s) reaction conditions showed higher selectivity to H2O2 or water H2O, respectively. The selectivity of 80 % to H2O2 was achieved for the N–C–MW-800W-140s sample at the potential of 0.6 V vs RHE at the catalyst loading of 0.05 mg/cm2. The results showcase the potential of MW carbonization in producing ORR electrocatalysts with diverse functionalization, leading to modified reaction selectivity that can be utilized in various electrocatalytic applications. Acknowledgments The research leading to these results was supported by the Johannes Amos Comenius Programme, European Structural and Investment Funds, project 'CHEMFELLS V‘ (No. CZ.02.01.01/00/22_010/0003004). References Yang, S. et al., Toward the decentralized electrochemical production of H2O2: A focus on the catalysis. ACS Catalysis, 2018.Bouleau, L. et al., Best practices for ORR performance evaluation of metal-free porous carbon electrocatalysts. Carbon, 2022.Wang, YX. et al., Quantifying environmental and economic impacts of highly porous activated carbon from lignocellulosic biomass for high-performance supercapacitors. Energies, 2022.Silva, R. et al., Efficient metal-free electrocatalysts for oxygen reduction: Polyaniline-derived N- and O-doped mesoporous carbons. Journal of the American Chemical Society, 2013.Oyharçabal, M. et al., Influence of the morphology of polyaniline on the microwave absorption properties of epoxy polyaniline composites. Composites Science and Technology, 2013. Figure 1

A comparative study between PVD-TiMgN and PVD-TiMgGdN sputtered coatings to evaluate the influence of Gd and its effect on the corrosion properties of the individual coatings

DC-PVD TiMgGdN coatings with excellent corrosion properties have been successfully developed using a powder metallurgy TiMgGd target while maintaining the well known tribological properties of TiN. In this study, TiMgGdN coatings were compared with TiMgN coatings using identical deposition parameters to investigate the influence of Gd on the corrosion behavior. For this purpose, a TiMg powder metallurgical target was used with an identical Ti/ Mg ratio as the TiMgGd target. The coatings were comprehensively analysed by different analytical methods such as X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), X-Ray Photonelectron Spectroscopy (XPS) and Glow Discharge Optical Emission Spectroscopy (GDOES) regarding their chemical, structural and microstructural characteristics. The corrosion properties were investigated using the neutral salt spray test (NSS test) in 5 % NaCl solution as well as with potentiodynamic tests in 0.5 % NaCl solution saturated with Mg(OH)2.Based on the findings of this study, it can be concluded that the excellent corrosion performance along with the mechanical properties are supported by the Gd addition to the coatings. The TiMgN coatings show a change in chemical composition, microstructure as well as in hardness after corrosive exposure, which cannot be observed on TiMgGdN coatings. Consequently, alloying TiMgN with Gd maintains the stability of the coating during corrosive exposure. The analytical results show that the excellent corrosion performance and stability of the TiMgGdN coatings are due to a stable and stronger passivation layer by the formation of Mg(OH)2 and Gd2O3 on the TiMgGdN surface. Furthermore, the Gd2O3 contributes to a strong hydrophobic effect. Regarding the microstructure, TiMgGdN coatings are seemingly denser compared to the TiMgN coatings, which positively influences the corrosion resistance of this coating.

Reconstructing interfacial manganese deposition for durable aqueous zinc-manganese batteries.

Low-cost, high-safety, and broad-prospect aqueous zinc-manganese batteries (ZMBs) are limited by complex interfacial reactions. The solid-liquid interfacial state of the cathode dominates the Mn dissolution/deposition process of aqueous ZMBs, especially the important influence on the mass and charge transfer behavior of Zn2+ and Mn2+. We proposed a quasi-eutectic electrolyte (QEE) that would stabilize the reversible behavior of interfacial deposition and favorable interfacial reaction kinetic of manganese-based cathodes in a long cycle process by optimizing mass and charge transfer. We emphasize that the initial interfacial reaction energy barrier is not the main factor affecting cycling performance, and the good reaction kinetics induced by interfacial deposition during the cycling process is more conducive to the stable cycling of the battery, which has been confirmed by theoretical analysis, quartz crystal microbalance with dissipation monitoring, depth etching X-ray photon-electron spectroscopy, etc. As a result, the QEE electrolyte maintained a stable specific capacity of 250 mAh g-1 at 0.5Ag-1 after 350 cycles in zinc-manganese batteries. The energy density retention rate of the ZMB with QEE increased by 174% compared to that of conventional aqueous electrolyte. Furthermore, the multi-stacked soft-pack battery with a cathodic mass load of 54.4mg maintained a stable specific capacity of 200 mAh g-1 for 100 cycles, demonstrating its commercial potential. This work proves the feasibility of adapting lean-water QEE to the stable aqueous ZMBs.

Hollow BiOI/Bi5O7I hierarchical microsphere with S-scheme heterostructure for efficiently removal of tetracycline hydrochloride

The problem of environmental pollution caused by the frequent use of antibiotics has attracted extensive attention. The heterojunction composed of various bismuth oxyiodide (such as BiOI, Bi4O5I2, Bi5O7I, etc.) were widely used in the treatment of antibiotic wastewater. Herein, a hollow BiOI/Bi5O7I hierarchical microsphere was constructed in-situ by annealing BiOI precursors synthesized by the solvothermal method. The phase transition temperature for the formation of heterojunctions has been investigated in detail. The obtained products were characterized by various technologies including transmission electron microscope (TEM), X-ray photon-electron spectroscopy (XPS), and so on. Experimental results suggested that 390-BiOI/Bi5O7I microsphere with hollow structure exhibits the optimal performance and maximum photocurrent response under visible light irradiation. The efficiency for degradation of tetracycline hydrochloride (TH) was up to 83 % in 100 min. The value still maintained at 95 % after the catalyst has been reused for four times. The capture experiment indicates that produced ·O2− played the most important role. But formed h+ and ·OH played a secondary role. The degradation intermediates were analyzed by Liquid Chromatography-Mass Spectrometry (LC-MS). Accordingly, the possible degradation pathways are proposed. An S-scheme based heterostructure photocatalytic mechanism is proposed aiming to explain the enhanced catalytic performance. The BiOI/Bi5O7I heterojunction with exceptional activity and stability is bound to expand applications in the field of water treatment.

Room-temperature fabrication of a heterostructure Cu2O@CuO nanosheet electrocatalyst for non-enzymatic detection of glucose and H2O2

• Binder-free Cu 2 O@CuO nanosheets were deposited on FTO using vacuum kinetic spray at room temperature. • Cu 2 O@CuO nanosheets exhibited high sensitivity toward detection of glucose at 818.5 μA·mM −1 ·cm −2 . • Cu 2 O@CuO nanosheets exhibited wide linear detection range of glucose from 0.02 to 5 mM. Heterostructure Cu 2 O@CuO nanosheets are spontaneously formed during the kinetic-spraying of nanostructured CuO thin film on the fluorine-doped tin oxide (FTO) substrate at room temperature under low vacuum conditions by the NPDS technique. The Cu 2 O@CuO nanosheets fabricated as a heterogeneous electrocatalyst are utilized for free enzyme detection of glucose and H 2 O 2 in 0.1 M NaOH, whereby the synergy between the multivalent copper species (I and II) results in an overall improvement of electrocatalytic performance. The in-situ formation of interfacial Cu 2 O@CuO heterostructure is verified using a high-resolution transmission microscope and X-ray photon electron spectroscopy. The fabricated electrocatalysts exhibit high sensitivity toward glucose oxidation of 818.5 μA·mM −1 ·cm −2 with a wide linear detection range extending from 0.02 to 5 mM and a limit of detection (LOD) of 5.8 μM. Also, the heterostructure Cu 2 O@CuO nanosheets show a very wide linear detection range of H 2 O 2 oxidation from 0.02 to 11 mM with a good detection sensitivity of 168 μA·mM −1 ·cm −2 and a LOD of 8.75 μM. The long-term stability for around 30 min and high oxidation selectivity with other interfering species are verified. Furthermore, Cu 2 O@CuO nanosheets exhibit higher catalytic rate constant and diffusion coefficient toward glucose species compared with H 2 O 2 .

(Invited, Digital Presentation) Fundamental Understanding and Challenges in Cathode Materials for Next Generation Li-Ion Batteries

Introducing high-performance Li-ion batteries in current energy storage technologies has great hope in achieving decarbonization goals for sustainable future. The impact of Li-ion batteries in current energy sector is huge, especially portable electronics to electric vehicles. With this energy demand, recently, researchers have been exploring the so-called “Li-rich anion redox” cathode chemistry, in which electrons stored on oxide anions are reversibly utilized during redox reaction along with conventional transition metal redox to obtain high energy storage capability.1-2 Compared to conventional cathodes, the anion redox cathode chemistry is not straightforward as it goes through a complex redox reaction pathway, leading to fundamental issues such as voltage fade, voltage hysteresis and irreversible oxygen release. However, these anionic redox reactions in transition metal oxide-based cathodes attained by extracting excess lithium ions have resulted in stability issues due to weak metal (M) – oxygen(O) ligand covalency.1 In order to increase the tightness between metal–ligand, an alternative strategy was investigated by replacing M–O framework with M–X (X- S, Se) ligands. Based on the experimental studies, it is found that the metal-ligand tunability is the key to achieve highly reversible chalcogen anion redox reactions in various Li based chalcogen cathode materials.3 Further, the lithiation delithiation reactions of cathodes are investigated using in-depth electrochemical analysis and the electronic as well as structural changes during electrochemical reactions are understood using detailed spectroscopy and microscopy characterization. Findings from this research will inspire Ni and Co free chalcogen cathode design and various functional materials in the pursuit of next-generation cathode materials. In parallel, this presentation will also focus on fundamental understanding and importance of fabricating rechargeable high-temperature Li-ion batteries for various demanding applications such as military applications, sensor applications, oil and gas industry drilling applications. In this work, high temperature compatible electrode materials are identified, and their electrode/electrolyte interfacial stability issues at different depth levels are understood using energy tunable X-ray photon electron spectroscopy and further visualized with advanced microscopy imaging. This proof-of-concept study will lead to a new paradigm for transforming ambient temperature Li-ion battery technology to high-temperature applications.

Electro fabrication of molecularly imprinted sensor based on Pd nanoparticles decorated poly-(3 thiophene acetic acid) for progesterone detection

In recent years, scientific community has witnessed substantial interest in the design and engineering of electrodes as sensing platforms towards sensitive and selective detection of hormones. An electrochemical strategy for the detection of progesterone was proposed by generating a composite film comprising of palladium nanoparticles with 3-thiophene acetic acid (3-TAA) coupled with molecular imprinting technology. Progesterone molecule was employed as the template while generating molecular imprints by electropolymerization on the surface of the Carbon Fibre Paper (CFP) electrode. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry were used to analyse the various modified working electrodes (CV). Characterization methods included field emission scanning microscopy, energy dispersive X-ray spectrometry, optical profilometry, and X-ray photon electron spectroscopy. Pd nanoparticles resulted in enhanced sensitivity and molecular imprinting technology contributed to its specificity. Because of the molecular cavities created on the removal of the template molecule, Nyquist plots data showed that the MIP/Pd/CFP electrode had the lowest charge transfer resistance compared to other control electrodes.

Synthesis of functional hydrochar from olive waste for simultaneous removal of azo and non-azo dyes from water

Industrial wastewater effluent containing dyes and hazardous waste, such as olive waste, pose serious threat to health and environment. This work investigated the removal of azo and non-azo dyes from a single and binary aqueous system using hydrochar produced from hazardous olive waste using hydrothermal carbonization (HTC). Optimisation suggested hydrochar obtained at 250°C (HC-9) exhibited best physiochemical, structural properties and around 300% increase in carboxylic and carbonyl groups indicated by nuclear magnetic resonance spectroscopy. HC-9 removed ∼100% of Methylene blue and Congo red in single (120 and 180 min) and binary system (60 min), respectively. Ex situ X-ray photon electron spectroscopy and surface area analysis after adsorption suggested chemisorption supported by pseudo-second order reaction, Langmuir, and Redlich-Peterson model. HC-9 exhibited around 80% reusability in three adsorption cycles. Thus, better working efficiency of our hydrochar in the complex wastewater make it a potential candidate to be employed in commercial plants.

Electrodeposited PdNi on a Ni rotating disk electrode highly active for glycerol electrooxidation in alkaline conditions

The development of alcohol-based electrolysis to enable the concurrent production of hydrogen with low electricity consumption still faces major challenges in terms of the maximum anodic current density achievable. Whilst noble metals enable a low electrode potential to facilitate alcohol oxidation, the deactivation of the catalyst at higher potentials makes it difficult for the obtained anodic current density to compete with water electrolysis. In this work the effect of significant parameters such as mass transport, glycerol and OH− concentration and electrolyte temperature on the glycerol electrooxidation reaction (GEOR) in alkaline conditions on a bimetallic catalyst PdNi/NiRDE (Pd0.9Ni0.1) has been studied to discern experimental conditions which maximise achievable anodic current density before deactivation occurs. The ratio of NaOH:glycerol in the electrolyte highly affects the rate of the GEOR. A maximum current density of 793 mA cm−2 at -0.125 V vs. Hg/HgO through steady state polarisation curves was achieved at a moderate and intermediate rotation rate of 500 RPM in a 2 M NaOH and 1 M glycerol (ratio of 2) electrolyte at 80 °C. Shown here is a method of catalyst reactivation for enabling the long-term use of the PdNi/NiRDE for electrolysis at optimal conditions for extended periods of time (3 h at 300 mA cm−2 and 10 h at 100 mA cm−2). Through scanning electron microscopy (SEM), X-ray photon electron spectroscopy (XPS) and X-ray diffraction (XRD) it is shown that the electrodeposition of Pd and Ni forms an alloy and that after 10 h of electrolysis the catalyst has chemical and structural stability. This study provides details on parameters significant to the maximising of the GEOR current density and the minimising of the debilitating effect that deactivation has on noble metal based electrocatalysts for the GEOR.

Viability of Activated Carbon Derived from Polystyrene Sulphonate Beads as Electrical Double Layer Capacitors

In this paper, a commercial polymeric resin precursor (polystyrene sulphonate beads) was used as a source of carbon spheres. The resin was pyrolyzed at different temperatures (700, 800, and 900 °C) and the resulting carbons were analyzed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). From the result of EIS, carbon spheres obtained at 700 °C (CS−700) have the least ohmnic resistance and highest capacitance. In furtherance, the resin was chemically activated with iron (III) chloride FeCl3·6H2O at different concentration (0.1 M, 0.3 M, and 0.5 M) and pyrolyzed at 700 °C to obtain activated carbon sphere namely (ACS 700−0.1, ACS 700−0.3, and ACS 700−0.5) in which the last digit of the samples denotes the concentration of FeCl3. Scanning electron microscope (SEM) showed that the carbon is of spherical shape; X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and X-ray photon electron spectroscopy (XPS) revealed successful introduction of Fe on the surface of the carbon. Out of all the activated carbon spheres, ACS 700−0.1 exhibited highest double layer capacitance of 9 µF cm−2 and lowest charge transfer resistance of 3.33 KΩ·cm2. This method shows that carbon spheres obtained from a polymeric source can be easily improved by simple resin modification and the carbon could be a potential candidate for an electrical double layer capacitor.

Superconducting interstitial MoReRuCx medium-entropy alloys with a hexagonal structure

We report the results of structural and physical studies on the MoReRuCx medium-entropy alloys (MEAs) with x varying from 0 to 0.20. In the whole x range, a single hexagonal phase is formed. The variation of lattice parameters indicates that carbon atoms are located at the interstitial site for x ≤ 0.10 while occupy both the interstitial and substitutional sites at higher x values, which is corroborated by the x-ray photonelectron spectroscopy (XPS) results. Moreover, the resistivity, magnetic and thermodynamic measurements evidence that these MEAs are bulk fully gapped superconductors. In particular, the transition temperature Tc displays a dome-like dependence on carbon content with a maximum of 9.62 K at x = 0.05, whereas a maximal zero-temperature upper critical field Bc2(0) of 10.5 T is achieved at x = 0.10. For all MEAs, the specific heat data reveal the existence of an inhomogeneous superconducting state, which is discussed in relation to the chemical inhomogeneity and strong atomic disorder. In addition, we show that the key factors that control superconductivity are essentially the same for both MoReRuCx and ReCx, despite their very different Tc values. Our work not only provides the first series of interstitial MEAs with a hexagonal structure, but also demonstrates a feasible way to tune the superconductivity in multicomponent alloys.

Dynamic structure of highly disordered manganese oxide catalysts for low-temperature CO oxidation

The dynamic structures of a highly disordered manganese oxide catalyst (HDMO) and intermediates were thoroughly studied from precursor to working catalyst. Excellent CO oxidation activity at low temperatures (T50 = 83 °C) was performed over a HDMO in the presence of H2O and CO2. The specific reaction rate of 4.56 μmolCO·gcat−1·s−1 at 90 °C was approximately 25 times and 15 times higher than those of bixbyite-type α-Mn2O3 and cryptomelane-type α-MnO2, respectively. With X-ray photon electron spectroscopy (XPS), we reveal that more surface oxygen vacancies (Ov) and adsorbed oxygen species from the highly disordered structure could promote the redox property and oxygen release capability. In situ Raman and DRIFTS spectroscopy were used to identify a dynamic surface phase transformation during CO adsorption and oxidation. In combination with kinetic studies of CO oxidation, we conclude that there are two mixed mechanisms for CO oxidation over HDMO: the Langmuir-Hinshelwood (L-H) mechanism and the Mars-van Krevelen (MvK) mechanism.

Molecularly Imprinted Scaffold Based on poly (3-aminobenzoic acid) for Electrochemical Sensing of Vitamin B6

Inadequate or excess consumption of Vitamin B6 (Vit B6) can have ill effects on the overall well-being of humans, thereby making it necessary to control their content and composition in the food we consume. A simple sensor is fabricated in this work for Vit B6 detection based on employing an electropolymerized molecularly imprinted polymer (MIP) of 3-amino benzoic acid. The poly (3- aminobenzoic acid) (P-(3ABA)) film was electrodeposited by potentiodynamic cycling of potential with and without Vit B6 (template) on carbon fiber paper electrode (CFP). The modified working electrodes were characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Field emission scanning microscopy, Energy dispersive X-ray spectrometry, Fourier Transform Infrared spectroscopy, Optical profilometry and X-ray photon electron spectroscopy were used for characterization. Nyquist plots revealed least charge transfer resistance at MIP/CFP than other control electrodes due to the molecularly imprinted sites. Under the optimized experimental conditions the developed MIP sensor showed a linear range 0.6 μM to 700 μM, with a detection limit of 0.010 μM. Also a value of the imprinting factor (β = 3.50) indicates very good selectivity of the prepared sensor towards Vit B6 detection over its structurally similar analogues in the analysis of real sample matrices.

Red-emission analysis, Judd–Ofelt intensity parameters and laser properties of CdMgZnO:xEu3+ nanocrystals: the effects of Eu3+ concentration

In this paper, we discuss a strong red Eu3+-concentration-dependent emission line associated with an electric dipole transition (5D0 → 7F2) at 616 nm in CdMgZnO:xEu3+ nanocrystals made via a sol–gel synthesis route. Oxygen interstitial defects created by the presence of a mixed-valence state of Eu 3+ and Eu2+ ions as rare-earth cations lead to a structural distortion which is confirmed by x-ray photon electron spectroscopy. The Judd–Ofelt intensity parameters, Ω2 and Ω4, obtained from the emission spectra, show a trend for Ω2 > Ω4 that translates to stronger covalence and a stable local structure surrounding the Eu3+ ions in CdMgZnO nanocrystals. The asymmetry ratio (R o), radiative lifetime (), branching ratio , stimulated emission cross-section, and the gain bandwidth (δ e× Δλ eff) for 5D0 are computed and analysed. A radiative lifetime ranging from 789 to 984 µs points to a suitable material for orange-red fluorescent phosphors for lighting and display technologies. The gain bandwidth (δ e× Δλ eff), which is dependent on the Eu3+ concentration, suggests the use of the CdMgZnO:xEu3+ nanocrystal material in fibre amplifiers, while the sample with x = 1.5%, which yields the largest emission cross-section (15.79 × 10−22 cm2), the highest gain bandwidth (28.8 × 10−28 cm3), and a high branching ratio (71%), is the best candidate for red laser applications.

Insights into the biomechanical properties of plasma treated 3D printed PCL scaffolds decorated with gold nanoparticles

Tissue engineered constructs having desired biomimetic and mechanical properties emerged due to the complexities involved in conventional skin grafting. They facilitate tissue regeneration without compromising mechanical properties. Herein, we report the fabrication of polycaprolactone (PCL) scaffold by fused deposition modeling and immobilization of gold nanoparticles onto the polymer surface after modifying the PCL surface using plasma polymerization. 3D printed PCL scaffolds inlaid with gold nanoparticles (Au-PCL) were characterized for their structural and mechanical properties using FESEM, and nano-indentation. The surface chemistry was analyzed using X-ray photon electron spectroscopy (XPS), wettability was determined using water contact angle studies and surface topography was imaged by atomic force microscopy (AFM). The surface modification of 3D printed scaffolds significantly improved their hydrophilicity suggesting that hydrophobicity which restricts the use of PCL in biological applications could be overcome by plasma modification. Nanoindentation studies showed that Au-PCL scaffolds exhibited remarkable enhancement in mechanical properties with reduced Young's modulus of 1.81 GPa. Biocompatibility was assessed by measuring cell viability, cell attachment and immune response. In vitro biocompatibility studies indicated good attachment of viable cells onto the gold nanoparticles incorporated 3D printed network. Immune response studies indicated that scaffolds did not enhance the production of pro-inflammatory cytokines such as TNF-α, IL-8 and IL-β. Collectively, plasma modification and surface immobilization of gold nanoparticles onto the 3D printed PCL scaffold is a simple and cost-effective technique to enhance the mechanical properties and biocompatibility of hydrophobic scaffolds like PCL, thereby making this technique a very promising tool for futuristic applications of scaffolds.

Inducing upwards band bending by surface stripping ZnO nanowires with argon bombardment

Metal oxide semiconductors such as ZnO have attracted much scientific attention due their material and electrical properties and their ability to form nanostructures that can be used in numerous devices. However, ZnO is naturally n-type and tailoring its electrical properties towards intrinsic or p-type in order to optimise device operation have proved difficult. Here, we present an x-ray photon-electron spectroscopy and photoluminescence study of ZnO nanowires that have been treated with different argon bombardment treatments including with monoatomic beams and cluster beams of 500 atoms and 2000 atoms with acceleration volte of 0.5 keV–20 keV. We observed that argon bombardment can remove surface contamination which will improve contact resistance and consistency. We also observed that using higher intensity argon bombardment stripped the surface for nanowires causing a reduction in defects and surface OH– groups both of which are possible causes of the n-type nature and observed a shift in the valance band edge suggest a shift to a more p-type nature. These results indicate a simple method for tailoring the electrical characteristic of ZnO.

Structural, morphological and electrical properties of Sm-Gd Co-doped ceria thin films for micro-solid oxide fuel cells

Thin film electrolytes of Sm and Gd doubly co-doped ceria, namely, Ce0.8Sm0.1Gd0.1O1.90 (CSGO) deposited by pulsed laser deposition (PLD) technique have been investigated. The influence of oxygen partial pressure (pO2) on structural and morphological properties of CSGO thin films deposited on Si (111) substrate was studied by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscope (FESEM) and atomic force microscopy (AFM) techniques. The XRD and FESEM results showed that the films were polycrystalline cubic structure with (111) oriented columnar structure. The co-doping strategy has strongly helped to stabilize the Ce4+ state as the lattice parameter of the films did not show any significant change under the influence of pO2 in the range of 2 × 10-4-3 × 10-2 mbar. The electrical conductivity and activation energy of CSGO thin film supported on NiO-GDC10 anode were found to be 0.48 mS.cm−1 and 0.5 eV respectively. Determination of significantly lower Ce3+ concentration (27%) in CSGO film by X-ray photon electron spectroscopy (XPS) suggests that Sm-Gd co-doping has strongly suppressed the conversion of Ce4+ to Ce3+ in the overall composition.

Hydrophilic hierarchical carbon with TiO2 nanofiber membrane for high separation efficiency of dye and oil-water emulsion

Hierarchical carbon hybrid materials have gained more attention in recent times especially in the separation of pollutants from wastewater. In this study, a novel ternary composite of graphitic carbon nitride (G-C3N4) decorated on reduced graphene oxide (RGO) with titanium dioxide (TiO2) nanohybrids was synthesized using hydrothermal approach to modify the electrospun PVDF membranes for the separation of oil and dye in wastewater. The characteristic functional groups of G-C3N4, RGO and TiO2 (G-C3N4,/RGO/TiO2) nanohybrids were confirmed by X-ray diffraction (XRD) and X-ray photon electron spectroscopy. Moreover, the prepared membranes were also studied using field emission scanning electron microscope and X-ray photoelectron spectroscopy. Interestingly, the PVDF modified membranes displayed excellent thermal stability with lower contact angle, increased surface roughness and surface charges. It was due to the tunable covalent π-π interfaces among G-C3N4 and RGO 2D hierarchical structured nanosheets. Besides due to the reasonable hierarchical structure formation of chemical and physical defense mechanism, the modified membranes exhibited outstanding antifouling performance and different oil water emulsion rejections. The pure water flux for GT-4 membrane was around 1261.2 ± 2 L/m2.h and exhibited high oil water removal efficiency above 95.4 ± 0.1% for different oils. The modified PVDF membranes also exhibited higher rejection rate of about 94.2 ± 0.5% for methylene blue dye removals. These studies confirm the formation of hydration layer and hierarchical structure for membranes which can be employed in oil water emulsion separation and dye rejection studies.

Si and Si@C Nanoparticles for Lithium-Ion Batteries Anodes: Electrode/Electrolyte Interface Evolution

Due to increasing demand in energy storage, much attention has been paid to Si as an anode material in Li-Ion batteries because of its theoretical capacity (3579 mAh/g in the Li15Si4 alloy vs 372 mAh/g for graphitic carbon). However, silicon suffers from several drawbacks, including rapid pulverization and SEI ripening, limiting its use. Nanostructuration and protection of silicon with a carbon coating are proven methods to improve the behavior of silicon-based anodes [1]. Using the laser pyrolysis method, the synthesis of silicon-carbon core-shell nanoparticles was achieved in a continuous way, without intermediate manipulations between the synthesis of the core from silane precursor and the shell from ethylene [2].The influence of the carbon coating on electrochemical performances was studied in coin cells in operando conditions by using electrochemical impedance spectroscopy (EIS) as well as post mortem analysis of the anode by using (X-Ray Photon electron Spectroscopy (XPS), Scanning Electron Microscopy (SEM) and High Resolution Transmission Electron Microscopy (HRTEM)). Special attention was paid to the first cycle because of its major importance in the formation and growth of the SEI and the long term behavior of the battery. By comparing measurements on Si and Si@C materials, EIS clearly demonstrates the beneficial effect of the carbon shell in the SEI stabilization. The stability of the the SEI resistance shows the protective effect of the the carbon shell while the SEI resistance is strongly modified and increases during lithiation. Such behavior can be related to the evolution of the chemical composition determined by XPS at different potentials during lithiation and delithiation. Figure 1

Physical reduction of graphene oxide for supercapacitive charge storage

The oxygen-containing functional groups in graphene oxide (GO) impose considerable limitations in their applications requiring chemical inertness and electrical conductivity such as supercapacitive charge storage. Chemical reduction of GO has been frequently employed; however, processing of large volume of hazardous solvents impose severe environmental concerns. This article demonstrates the optical reduction of freeze dried GO into reduced GO (rGO) by a computer controlled laser engraver as a plug and operate device. The conversion of GO into rGO as a function of laser powers has been monitored by X-ray diffraction, X-ray photon electron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, Thermogravimetric analysis, and field emission scanning microscopy. The rGO thus produced has been evaluated for their charge storage capability in aqueous electrolytes. The best performing laboratory prototype demonstrated one of the best energy density of rGO electrodes in an aqueous electrolyte. The promising properties of the supercapacitors thereby developed as well as cost effectiveness and potential for large scale production engaging laser engraving process, the present work offers numerous potentials for deploying efficient and low cost supercapacitive devices.